1. Field of the Invention
The present invention pertains to a device and method for providing non-invasive intraoral electromuscular stimulation to a patient to treat a breathing disorder, such as obstructive sleep apnea, and, in particular, to a device and method wherein electromuscular stimulation is provided to the patient at a time prior to the onset of inspiration and continues through a major portion of the inspiratory phase and is applied at a level sufficient to induce muscle contraction without pain and/or is provided bilaterally at sublingual locations posterior to the frenulum in an anterior-to-posterior and/or posterior-to-anterior direction.
2. Description of the Related Art
Obstructive sleep apnea (OSA) is a medical condition in which the upper airway is repeatedly occluded during sleep despite continued respiratory effort. Those afflicted with OSA experience sleep fragmentation and complete or nearly complete cessation of ventilation intermittently during sleep with potentially severe degrees of oxyhemoglobin desaturation. An OSA sufferer typically experiences many apnea and/or hyponea events throughout the night. During an apnea event, the resulting hypoxia typically progresses until arousal occurs, which reestablishes airway patency.
Symptoms of OSA include snoring, choking and/or gasping during sleep, fragmented sleep, daytime sleepiness, fatigue and poor concentration. Airway obstruction can lead to a reduction in tidal volume, oxygen desaturation and progressive increases in respiratory rate. The long-term effects of OSA may be translated clinically into extreme daytime sleepiness, cardiac arrhythmias, pulmonary-artery hypertension, congestive heart failure and/or cognitive dysfunction. Other consequences of OSA include right ventricular dysfunction, carbon dioxide retention during wakefulness, as well as during sleep, and continuous reduced arterial oxygen tension. Hypersomnolent sleep apnea patients may be at risk for excessive mortality from these factors as well as by an elevated risk for accidents while driving and/or operating potentially dangerous equipment.
Studies of the mechanism of collapse of the airway suggest that during some stages of sleep, there is a general relaxation of the muscles that stabilize the upper airway segment. This general relaxation of the muscles is believed to be a factor contributing to OSA. More specifically, it is generally understood that the patency of the airway depends on the activity of the pharyngeal dilator muscles. Common sites of obstruction are behind the tongue and at the level of the soft palate. In a normal state, the muscles of the tongue, the genioglossus, hyoglossus, styloglossus, palatoglossus and the superior, inferior, transverse and vertical linguals, act to protrude or retract the tongue. Posterior fibers of the genioglossus draw the base of the tongue forward and anteriorly. One or more of these muscles normally contract reflexively during inspiration. However, it is generally understood that OSA suffers experience a reduction of lingual muscle activity during sleep as compared to nonapneics, thereby causing a reduction in airway patency.
Several therapeutic remedies exist for treating OSA. The most invasive, yet most likely to be successful, is a tracheotomy, which creates an airway bypass around the site of obstruction. Other surgical remedies include removal of deformed, loose or swollen structures or tissues in the upper airway. It is also known to apply positive air pressure at the mouth and/or nose of the patient to xe2x80x9csplintxe2x80x9d the airway, thereby maintaining an open passage to the lungs. In addition, pharmacological solutions have also been pursued.
None of these therapies is successful in all cases. Surgical relief is invasive, introduces a potential for surgical complications and is appropriate in only a small percentage of cases. On the other hand, the nasal or nasal/oral mask needed to apply a positive air pressure is not tolerated by some OSA patients. Pharmacological therapies have been, in general, less than satisfactory, and side effects are frequent.
It is also been proposed to treat OSA by electrically stimulating the musculature of the upper airway to prevent its relaxation and/or induce contraction, thereby preventing or minimizing subsequent blockage of the airway. There are two methods in which electromuscular stimulation can be applied to a patient; invasively or non-invasively. Invasive electrical stimulation of a muscle involves implanting one or more electrodes, either permanently or temporarily within the patient. These subcutaneous electrodes are typically located on or near the nerves that control the muscle to be stimulated. In some applications, the electrodes are placed in direct contact with the target muscle. Subcutaneous electrodes positioned adjacent the muscle or on or near the nerve controlling the muscle to be stimulated have the benefit of focusing the electrical energy on the muscle/nerve to be stimulated.
However, electrical muscle stimulation utilizing implanted electrodes requires surgical intervention, the permanent presence of foreign materials within the patient""s tissue, and, in some applications, at least one electrical connection protruding from the patient. Consequently, there is a potential for infection or irritation at the surgical site and at the site where the electrode or electrical connection protrudes through the surface of the patient. In addition, it is reasonable to expect that some patients may be apprehensive about having a foreign object surgically placed within their body.
Non-invasive electrical stimulation of the muscles in the upper airway involves placing an electrode in direct contact with a surface of the patient and passing a current through the surface tissues adjacent the electrode. For example, U.S. Pat. No. 5,123,425 to Shannon et al. teaches applying an electrical stimulation to the exterior surface of the patient""s neck below the chin to induce contraction of the upper airway muscles. In addition, U.S. Pat. No. 5,792,067 to Karell teaches an intraoral device that applies electrical stimulation to the hard palate, soft palate or pharyngeal area to induce contraction of the upper airway muscles. U.S. Pat. No. 5,190,053 to Meer teaches an intraoral device that applies electrical stimulation to the genioglossus muscle via electrodes located on the mucosa on the floor of the mouth on either side of the frenulum, which is the connecting membrane under the tongue that attaches the anterior portion of the tongue to the floor of the mouth.
While each of these non-invasive stimulation techniques claim to achieve some degree of success in opening the airway, it not clear that they are successful in a sufficient number of patients to render any one of these techniques a viable replacement to the other conventional treatments discussed above.
In addition to using either invasive or non-invasive stimulation on a patient, conventional electromuscular stimulation treatments typically initiate stimulation in one of two alternative timing methods. In a first timing method, stimulation is applied only when needed to counteract a detected breathing disorder, for example, at the onset of an apnea or when snoring is detected. This technique has the advantages of, for example, conserving energy and minimizing muscle fatigue. However, it is not clear that this stimulation timing method is sufficiently successful in breaking an apnea or stopping snoring in a significant number of OSA sufferers to be suitable for widescale and/or practical use.
According to a second timing method, stimulation is provided independent of the occurrence of a breathing disorder, such as an apnea, snore or other symptoms of respiratory distress. In this second method, stimulation is typically provided during each inhalation phase of a patient""s breathing cycle and typically is initiated at the onset of inspiration. For example, U.S. Pat. Nos. 5,540,732 and 5,522,862 both to Testerman teach an invasive electrical stimulation system in which stimulation is applied to the patient in response to sensed inspiration. In an alternative method, such as that taught by U.S. Pat. No. 5,158,080 to Kallok, stimulation is provided at all times during the patient""s breathing cycle, i.e., during the entire inspiratory phase and the entire expiratory phase. Although some success has been claimed when stimulation is provided independent of the occurrence of a breathing disorder, it not clear that the degree of success of either technique is sufficient to warrant the use such a timing technique on a widescale basis.
Other investigators, such as R. P. Schnall et al., as indicated, for example, in an article entitled xe2x80x9cDilatory Effects of Upper Airway Muscle Contraction Induced by Electrical Stimulation in Awake Humans,xe2x80x9d published in Volume 75 of the Journal of Applied Physiology in 1995, pages 1950-65, have experimented with various stimulation techniques, including the timing at which stimulation is initiated and the corresponding placement of the electrodes within the patient. However, as concluded in this article, the stimulation techniques attempted by Mr. Schnall et al. were unsuccessful in decreasing the number of breathing disorder events occurring in the test patients.
Accordingly, it is an object of the present invention to provide an intraoral electromuscular stimulation device for treating a breathing disorder, such as OSA, that overcomes the shortcomings of conventional muscle stimulating devices. This object is achieved according to one embodiment of the present invention by providing an intraoral electromuscular stimulation device that delivers intraoral electrical stimulation to a patient to reduce or minimize airway closure. In one embodiment of the present invention, the electromuscular stimulation device includes a first electrode and a first support member that sublingually supports the first electrode in a position posterior to the frenulum and generally proximate to a first, second or third molar of the patient. The stimulation device also includes a second electrode and a second support member that sublingually supports the second electrode in a position posterior relative to the first electrode.
It is another object of the present invention to provide an electromuscular stimulating system for treating a breathing disorder that does not suffer from the disadvantages of conventional systems. This object is achieved by providing an electromuscular stimulating system that includes an intraoral electrode dental appliance and a stimulation unit associated therewith. The dental applicant includes a first electrode and a first support member that supports the first electrode in a sublingual position posterior to the frenulum and generally proximate to the first, second or third molar of a patient. The dental appliance also includes a second electrode and a second support member that supports the second electrode in a sublingual position posterior relative to the first electrode. The stimulation unit provides stimulating energy to a portion of the patient in an anterior-to-posterior or posterior-to-anterior direction via the first and second electrodes.
It is yet another embodiment of the present invention to provide a method of providing intraoral electromuscular simulation to the patient that overcomes the shortcomings of conventional electrical stimulation methods. This objects is achieved, according to one embodiment of the present invention, by providing a method that includes the steps of: (1) positioning a first electrode in a patient""s mouth such that the first electrode is sublingually supported in a position posterior to the frenulum and generally proximate to one of a first, second or third molar, (2) positioning a second electrode in the patient""s mouth such that the second electrode is sublingually supported in a position posterior relative to the first electrode, and (3) applying an electrical stimulation to a portion of the patient via the first electrode and the second electrode so that the stimulating current travels in either an anterior-to-posterior or a posterior-to-anterior direction in the patient.
It is a still further object of the present invention to provide an intraoral electromuscular stimulation device employing a stimulation technique that applies stimulation to the patient at an appropriate time, duration, location and energy level so as to achieve results that are an improvement over conventional methods. This object is achieved by providing an intraoral electromuscular stimulation device that includes a first electrode, a second electrode, a first support member that sublingually supports the first electrode on a first side of the patient""s mouth relative to his or her midline, a second support member that sublingually supports the second electrode in a posterior position relative to the first electrode on the same side of the patient""s mouth, a sensor that detects a respiratory parameter of the patient and outputs a signal indicative thereof, and a control unit operatively coupled to the sensor, first electrode and second electrode. The control unit receives the signal from the sensor, distinguishes between inspiration and expiration of a patient based thereon, and initiates an electrical stimulation of the patient in an anterior-to-posterior or posterior-to-anterior direction via the first and the second electrodes at a start time prior to the onset of inspiration. The control unit also continues the stimulation through a portion of the inspiratory phase and provides the stimulation at a level that is sufficient to induce muscle contraction but is not sufficient to cause the patient pain.
It is still another embodiment of the present invention to provide a method of providing intraoral electromuscular simulation that applies stimulation to the patient at an appropriate time, duration and energy level so as to achieve results that are an improvement over conventional methods. This object is achieved, according to one embodiment of the present invention, by providing a method that includes the steps of: (1) positioning a first electrode and a second electrode in sublingual positions within a patient""s oral cavity on the same side of the patient""s mouth relative to the midline, with the second electrode being positioned posterior relative to the first electrode, (2) detecting a respiratory parameter of a patient and providing a signal indicative thereof, wherein the respiratory parameter is any monitorable physiological condition that can be used to differentiate between inspiration and expiration of the patient, and (3) applying an electrical stimulation to a portion of the patient between the first and second electrodes in a posterior-to-anterior direction or an anterior-to-posterior direction. In this embodiment of the present invention, initiating application of electrical stimulation occurs at a stimulation time prior to onset of inspiration, continues through a portion of the inspiratory phase and is provided at a level that is sufficient to induce muscle contraction but not cause the patient pain.
These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.